Clamp for stretching presses



March 18, 1947. P. E. FLOWERS CLAMP FOR STRETCHING PRESSES Original Filed Feb. 20, 1941 3 Sheets-Sheet l INVENTOR PAUL E. FLOWERS,

ATTORNEYS March 18 1947. P, FLOWERS 2,417,478

CLAMP FOR STRETCHING PRESSES Original Filed Feb. 20, 1941 3 Sheets-Sheet 2 INVENTOR PAUL E. FLOWERS,

ATTORNEY5 March 18, 1947. P. E. FLOWERS 7 2,417,473

CLAMP FOR STRETCHING PRESSES Original Filed Feb. 20, 1941 3 Sheets-Sheet 5 1 /7 20 r '4' I m -7' .INVENTOR AUL E. FLOWERS,

Swill, 16W

' ATTORNEYS Patentecl Mar. 18, 1947 2,417,478 .CLAMP FOR sTRE'rcmNG rnnssrs Paul E. Flowers, Mount Gilead, Ohio, assignor to The Hydraulic Development Corp. Inc., Wilmington, Del., a corporation of Delaware Original application February 20, 1941, Serial No. 379,875. Divided and this application December 26, 1941, Serial'No. 424,442

19 Claims. 1

This invention relates to presses of the type that employ mechanism for clamping the workpiece to the press. Certain types of sheet metal articles are economically fabricated by means of a stretching press in which a plain sheet of metal is bent at the proper places, and stretched in other places until the desired configuration of the article is obtained. It is necessary to secure opposite edges of the metal sheet to the press, and during the forming operation the operator causes a platen to move upwardly by fluid pressure against the under surface of the metal sheet or strip. The shape of the article is controlled in part by the amount of pressure exerted at the platen and also in part by the amount of slippage permitted at the jaws. After the distance This application is a division of my copending application, Ser. No. 379,875, filed February 20, 1941, now Patent 2,346,213, dated April 11, 1944.

In the prior art form of press it is usual to provide the same amount of slippage or full clamping effects over the entire length of one or both jaws therefore over the entire width of the metal strip. Under these conditions the number of shapes which can be formed in a press of this character is limited. When articles of intricate design are to be fashioned it may be necessary to provide full clamping effects at one or more points along the edge of the strip, and diflerent amounts of slippage at other points, On occasion, other special clamping and slipping effects must be provided in order to procure the desired stretched shape which may be a complicated design. For example, it may be necessary to move both halves of the jaws bodily either toward or away from the central stretching axis of the press, or in the case of a long jaw, to move only one end of the jaw with respect to the press or to move both ends of the jaw in opposite directions. In fact, the shapes into which a metal strip can be bent and stretched are almost without number when the press is operated by a skilled workman and the jaws are given universal movement as a body, and in addition can be adjusted as between jaw halves to allow any amount of slippage or full clamping effects at any point or points throughout the line of jaws.

Among the objects of the present invention is to provide a stretching press in which adjust- 2 Y ment can be made of the jaws asa complete body with respect to the other jaw body and with respect to the press.

Another object is to provide mechanism by which the jaw halves can be adjusted with respect to one another so as to obtain any desired clamping or slipping effect at any point throughout the length of each jaw.

These two objects are carried out. in brief, by subdividing each jaw into a number of individually adjustable clamping blocks mounted on a support which can be 'swung in the horizontal plane, and also moved in relation to the vertical axis of the Press.

In order to provide for full gripping effect 0 the strip, i. e., without any slippage whatsoever, it has been customary to employ a two-part jaw in which the gripping surfaces of the jaw are provided with a knife edge or its equivalent. This edge exerts a compressional force of an intense character over a line contact across the metal strip. The strains caused by these gripping forces may be so high, in the case of powerful presses, as to tear the metal. The same condition arises even when the jaws are corrugated or grooved in a criss-cross or diagonal manner, because the clamping forces are concentrated at one or more limited areas of the metal. Consequently, another object of the present invention is to provide an improved stretching press jaw in which the tearing effect on the metal is reduced to a minimum, even when the stretching forces and the necessary gripping effects to counteract these forces are considerable.

This object is carried out, in brief, by providing the clamping blocks, referred to hereinbefore, with perfectly smooth gripping surfaces,- these surfaces being arranged parallel to one another and to the metal strip. In order to obtain flat contact with the strip over the entire gripping surface of each block, a toggle mechanism is provided that permits the blocks to move with re. spect to one another and with respect to the metal strip, these movements being constrained to parallel paths. Thus a line or a point contact with the strip anywhere throughout the jaw is avoided. The blocks are initially held lightly in contact with the strip, and the operation of the toggle mechanism is such that a pull on the metal strip will cause the jaw blocks to move toward one another in parallel paths, thus to exert a clamping effect on the strip in proportion to the pull on the strip by the moving platen.

Still another object is to provide a conveniently operated structure, simple in design, for simultaneously opening the jaw blocks in order either to insert a metal strip or to remove-the stretched piece of metal. This object is attained by mounting the blocks on a common support. This support is actuated by a suitably positioned lever in v such a direction thatthe blocks are caused to frame. from its normal vertical position would cause a compression of one of the springs. depending on move abouttheir toggle connection and thus to 7 recede from one another and to leave a space between the jaw surfaces so as to permit the strip to be removed from the jaw without effort. It is therefore apparent that the clamping blocks are individually adjustable with respect toone reference is made to the following specification and the accompanying drawings. 1 1 Figure 1 is a longitudinal section of a stretching press, including the improved jaws.

Figure 2 is a plan viewof the press with a portion broken away. I

Figure 3 is a sectional view of the clampin jaws, taken along the line 33 in Figure 2. Figure 4 is a sectional view takenalong the line 4-4 in Figure 3. s

Figure.5 is an enlarged sectional view of the jaws, taken along the line 55 in Figure 2. This figure shows the left-hand pair of jaws in elevation more fully to illustrate the toggle connection between the jaws. 1

Referring more particularly to Figure .1, the frame of the machine is constituted of long flat pressure fluid in these cylinders being controlled which side of the vertical position the cylinderis moved. I I

Construction of the jaws The strip I 2, after passing over the platen 5,

is gripped at each end or side by a jaw assembly,

generally designated I5. The jaws are shown in section in Figures 3, 4 and 5 and in plan in Figure 2'. Each jaw takes the shape of a'rail-like or base member, indicated at l6, which preferably extends along the entire width of the machine so that the jaws canaccommodate the minimum width of, strip. The rail member I6 is channeled at the top to provide a large rectangular upwardly extending opening having undercut side walls extending along the entire lengthof the'rail memberand is adapted to receive a plurality of blocks, generally designated l8, constituted of a tough metal such as nickel steel. As shown in Figure 2, the length ofthe railmember I6 is divided into a large number of the block units l8, andthere are two rows of the block units filling the opening H. The innermost surfaces of the blocks I 8 are perfectly smooth, pref erably ground, and when placed in position these surface are exactly parallel to one another and metal plates, indicated at |,'which are supported at each end on an inclined webbed member 2 provided at the bottom with feet 3. The framework is closed at each side of the platesby means of a metal wall 4. The die or punch of the press is shown at 5, this die being bolted or otherwise removably secured to a long and heavy block 6 carried at both ends on pistons 1, which are adapted to reciprocate in a pair of cylinders 8. The pistons or rams 1 preferably terminate at the top in fiat surfaces to which the block 6 may be fixedly secured.

The cylinders 8 are hung on the trunnioned bearings lllwhich are carried at the ends of the webs ll, extending outwardly from the walls 4 of the frame. Thus the cylinders 8 are adapted to be rotated in the vertical plane at the trunnions.

The metal strip which is undergoing the stretching operation is indicated at l2 and extends over the upper surface of the die 5, the latter being suitably rounded, as indicated, in order to avoid cutting the metal. Itis apparent that when hydraulic pressure is applied to the cylinders 8, in a manner to be described hereinafter, and assuming that one of the rams 1 moves upwardly at a faster rate than the other ram, the cylinder which shows the greater'ram'movement will tendto rotate at the pivot l0 and moveto a positionsuch as to cause the load to be divided equally with the other ram. In order to maintain thecylinders in a normally vertical position, there may be inter posed between each cylinder and the'walls of the frame a compression spring, broadly indicated at l3, which is carried on a plate l4 bolted to the parallel to the strip contained between the surfaces. The blocks are held within the, opening H at their outer upper edges by means of an overhanging ledge 9 (Figures 3 and 5), which.

fits into a corresponding groove in the blocks.

Each block unit is subdivided into two rows each comprising a first or. inner row and a second 1 or outer row, indicated at 20 and 2|, which are spaced apart, as indicated at 22, by means of a pair of Parallel toggle levers or links 23 forming a parallelogram linkage. Each of these levers is constituted of a threaded rod 24 having a collar at the middle, the rod being received by cylindrically shaped metal elements 25 in cylindrical apertures 25. These elements fit snugly but slidably within partially cylindrical recesses which extend transversely of the blocks 20 and 2| in such a manner as to cause the blocks 20 to be, spaced from the opposite adjacent blocks 2|, as.

illustrated. The cylinders 25 and their openings preferably extend the entire width of each block.

Due to this toggle arrangement provided by'the.

cylindrical members 25 and their interconnecting rods24, the block or jaw 2| is adapted to move upwardly, but in moving upwardly the inner pair of blocks 2| is constrained to move inwardly, i. e.', Q

away from the outer blocks 20, due to the swivel action of the rod 24-cylinder-25 arrangement. In

setting up and adjusting the blocks there isa. space left between the inner surfaces of thev tact both sides of the strip, this movement ofthe T strip will cause the blocks 2| to move upwardly and inwardly to increase their clamping effects;

on the strip.

'The rectangular opening I1 is provided with ledge, indicated at 21, on which the two outermost sets of blocks 20 rest but ,leaving a space indicated at 28 directly belowthe inner sets of blocks 2|. The inner set of blocks 2| is maintained in its vertical position by resting on the upperends of the round-headed pins 29, which Thus any movement of either cylinder are received in the vertical openings 36 drilled in a smaller cross section, as indicated at 32, at the middle, and then flares outwardly at the bottom, as indicated at 33, to accommodate a relatively large recessed opening 34. There are two rows of openings 35 extending between the rectangular opening at the top of the rail member to the recessed opening 34 at the bottom of the rail member. These openings are positioned in line with the spaces 22 between the blocks 23, 2| on opposite sides of the strip l2. The openings 35 are positioned along the length of the rail member, one opening to each pair of blocks 26, 2|, and if the blocks are relatively long, then two or more openings per pair of blocks may be provided and symmetrically positioned with respect to each pair of blocks. These openings are adapted to receive bolts 36 of annular cross section, having bores 31 extending along the length of each bolt. Each bolt 36 terminates at its upper end in a flanged head, indicated at 36, the upper portion of which is provided with a hexagonal opening 39 which is adapted to receive a socket wrench (not shown).

The opposite adjacent inner surfaces of each pair of blocks 26, 2| are provided with a round opening indicated at 40, which is adapted to receive the flanged head 38. This opening terminates at the bottom of the blocks 2| in a ledge 4|, on which the flanged head 38 of the bolt 36 rests. However, the opening 40 extends for a greater depth into the block 20 so that no ledge is formed at this point, and the bolt 36 rests solely on the ledges formed in the blocks 2|. The purpose of this will be explained presently. The bolts 36 are threaded at their lower ends into a T-shaped bar 42, the horizontal portion of which is carried within the opening 34. The rail member I6 is provided with a longitudinally extending slot, indicated at 43, which receives the upwardly extending portion 44 of the bar 42. The bolts 36 are threaded into the bar 42 in such a manner as to leave a space 45 between the upper surface of the horizontal portion of the bar and the lower surface of the opening 34. A'space 46 is also left between the upper surface of the metal portion 44 and the lower surface of the slot 43. A mechanism which will now be described is provided for moving the bar 42 in a vertical direction in order to move the inner blocks 2| in a corresponding direction. This mechanism is generally indicated by the reference numeral 46', and is shown in detail in Figures 2, 3 and 4.

The rail member I6 is provided at a number of positions along its length (three as illustrated) with transversely extending openings 41 having a necked portion 48 and adapted to receive a shaft 49. The shaft is round for the greater portion of its length, but at a position directly above the metal portion 44 is turned down, as indicated at 50, to conform to a cam shape. Consequently the shaft at this position has a portion which corresponds to the true diameter of the shaft, and another portion which is arcuate in shape formed by a radius greater than the radius of the shaft. The latter is provided with a turned-down portion at one end which fits the smaller diameter part ofthe opening 41 and carries a washer II secured to the shaft by a nut 62. Thus-the shaft is prevented from moving in the longitudinal direction. At the opposite end the shaft is pinned to a hub 53 of a lever or actuating bar 64 which carries a connecting rod 66 secured to the levers 54 of the other two devices.

One of the shafts 49, the left-hand one as shown in Figure 2, may be extended beyond the hub 53, as indicated at 68, and secured to a handoperated lever 61. By moving the lever 61 in a vertical direction the shafts 43 of the three devices are caused to rotate (due to the interconnecting bar 55), thus causing the cam surfaces 66 of the shafts-to move either toward or away from the upper surface of the metal portion 44 (Figures 3 and 4), depending on the direction in which the lever 51 is moved. Directly below each cam surface 66 there is a wearing plate 63 of hardened metal secured by the screws 63 to a slot formed in the metal portion 44. Thus by rotating the lever 51 the T-shaped bar 42 can be moved upwardly or downwardly within the rail member l6, and if moved downwardly will cause the lower surface of the flanged portion 38 of the bolts 36 to exert a downward pressure on the ledges 4| of the inner blocks 2|, causing these blocks to move downwardly against the action of the springs 3|.

Due to the toggle arrangement 24, 25, this downward movement of the inner blocks 2| causes these blocks to move away from one another, thus decreasing the pressure exerted against the strip l2. If the lever 51 is rotated through a sufliclent angle, the inner blocks 2| will have moved outwardly to such an extent as to break all contact with the strip l2. Thus the latter can be readily removed from the jaws. It will be understood that there are as many of the jaw-loosening devices 46 at one side of the rail member l6 as may be necessary, depending on the length of the rail member, and it is further apparent that the rotation of the shafts 49 by the lever 51 causes the same outward movement of all of the individual blocks 2| on both sides of the strip l2, because the downward movement of the bar 42 exerts the same effect on all of the individual bolts 36 which rest on the ledges 4| of the individual jaw blocks. During the operation of the stretching press it may be desirable to permit a certain amount of slippage at'a particular point along the width of the metal strip, but to fully clamp other portions of the strip. In order to accommodate these different clamping and slipping effects it may be necessary to effect different adjustments at the bolts 36. It has been pointed out that as the bolts are tightened into the bar 42, the inner blocks tend to move away from one another, thus to permit any desired amount of slippage, and by tightening some of the bolts and loosening other bolts any opposite pair of jaws can be given a full clamping effect on the strip |2 or would permit any degree of slippage. It will be noted in this respect that each jaw block 2| is provided with its own adjusting bolt 36 so that the adjustment of the latter affects only its individual jaw block, thus providing a nicety of adjustment at each point along the width of the strip. In order to lock the bolts 36 in position after the individual adjustments have been made, a locking rod 60 which extends through the central bore 31 of each bolt may be provided. This rod is provided at its upper end with a screw driver head 6|, to which access can be had through the hexagonal opening 33. The lower end of the rod is threaded into a bar 62 which spans the lower end surface of the bolt 36, and is pinned as indicated at .63 to the bar 42. Thus by. tumingthe rod 66 at the head 6| alocking action is effected which prevents any movement of the bolt 36.

Mechanism ,for moving the jawrassembly as a unit toward and away from the platen on the plate I of the press, and which is reenforced by a number of diagonally extending ribs 65,, connecting the plate 64 with the outer surfaces of the rail member I6. Secured to the bottom surface of the plate 64 there is a pair of spaced downwardly extending box-shaped members 68 (Figure 1). A nut .69 is contained within each box member, and there is a rod 10 which is threaded in the nut. The latter preferably has a cylindrical shape, for purposes which will appear hereinafter, the axis of the cylinder being vertical (as seen in Figure 1) so that the rod 10 extends through the diameter of the cylinder. The purpose of this rod will be. explained hereinafter. The rod 10 has a shouldered portion indicated at I l where it passes through the inner wall of the box 66, and is secured to the box by a nut 12.

There is a pair of metal webs 13 secured to the under side ofthe box-shaped member 68 and therefore secured to the plate 64, these webs being provided with right-angle extensions, indicated at 14 and each of which has a. bore 15. Each plate 64 is provided with a groove at its inner edge indicated at 66 and on its underside for receiving the upwardly extending guides 16 of the longitudinal frame members 16'. A ram I1 passes through each bore 15 and is secured to the web 13 by a nut 18. Each ram is received in a hydraulically operated cylinder 19 at one end,

and at the other end is supported by a bracket lug 80 which is secured to the frame. It will be understood that there are two sets of cylinders 19 for each jaw unit l5 and consequently two box-shaped members 4, and two sets of the apreceives the pressure fluid.

In addition to providing mechanism for moving the jaw assembly as a unit toward and away from the platen, there is also provided structure for canting each of the jaw units This structure is shown to the extreme right of Figure land is designated generally by the reference numeral 85. Inasmuch as no claims are made on the specific canting mechanism, a, general description of the same will be suificient in order to complete the disclosure as a whole. This canting mechanism is controlled by a hand wheel I65 mounted on a shaft (not shown),-which is associated therewith through suitable keys and sprocket and chain structure indicated at I66, I

the arrangement being such that when the wheel remains in its neutral position each of the chains I06 is actuated to .move the two threaded rods 10 in equalamounts, thus causing the jaw l5 to be retracted throughout equal distances over its length.- However, when the wheel, for ex ample, is moved inwardly to the left as shown in Figure 1, only one of the sprocket andchain mechanisms will be actuated, which in turn will cause rotation of only one of the rods 10. Thus the jaw is caused to swing about the circular nut 69in a predetermined direction. By pulling out the hand wheel I05 and then rotating the same,

the other sprocket and chain mechanism is actuated, causing the other of the two rods to be rotated so as to swing the jaw IS in the opposite! direction. Thus the jaw I5 is adapted tov be moved toward or away from the platen 6 in such a manner that all parts of the jaw move through equal distances, or ifdesired the jaw may be canted in the horizontal direction-either to the effects onthe strip l 2.

There is a hand wheel I05 and its associated right or left in order to provide different holding I apparatus at each side of the machine in order to cant either one or both of the jaw assemblies ment which is determined by the size and shape of the strip to be stretched, also by the configura-,

tion into which the strip is to be stretched. In order to remove the slightest possibility of the adjusting mechanism obstructing the view of the operator during the stretching process, the bar and its hand wheel and sprocket mechanism can beswung at the'hubs 89, 96 from its'vertical to its horizontal position or beyond, and ifnecessary a well or other depression may be provided in the floor to receive the hand wheel and its associated apparatus. There is ordinarily no need to reinstate the bar 9| in its vertical position until either changes in the size of the strip or in the shape of the piece to be formed shall be required.

After the stretching operation thestrip in its formed shape is removed from the jaws 20, 2| by rotating the levers 51 (Figure 2) which as pointed Y out hereinbeiore, serves to move the jaws 2| outwardly away from the strip. The jaw assembly 7 26, 2| can then be returned to its initial position, ready for the insertion of a fresh metal strip, by

causingthe admission of pressure fluid to the pistons within the cylinders 19, thus moving them ofitwardly and carrying the jaw assemblies with t em.

From the foregoing it is evident that there is disclosed a stretching press having the greatest universality of use in that provision is made for permitting any amount of slippage or full clamp-.

ing effects at the jaw assemblies by individually adjusting the jaw blocks 2| at the bolts'36. The

refinement to which the slippage effects can be carried is determined solely by the number of individually adjustable blocksinto which the jaw assembly is divided. As another preliminary ad justment, there is also a means provided for cant- There is also provided a convenient means for releasing the strip from the jaws bysimply moving a pair of levers 51. It will be noted that pressure fluid is admitted separately to the cylinders 8 so that one end of the punch or die may, if desired, be moved at a faster rate than the other end in case it is necessary to form articles oicomplicated shape; The fact that the opposite ends of the platen 6 may be raised at different speeds is illustrated in Figure 2 by showing the front edge oi-the strip I! in a lower position than the rear edge l2. Under these' circumstances the slippage at that portion of the laws I! directly opposite the faster moving ram may be permitted. this slippage being brought about by individual adjustments of each set of blocks 20, 2 I Unequal stresses throughout the stretching cylinders are also relievedby the provision of mounting these cylinders 'on trunnions. Finally, all of the apparatus which serves to preliminarily adjustv the jaws may be swung away from the press so as to give the operator a clear view of the work during the stretching operation.

It will be understood that I desire to comprehend within this invention such modifications as come within the scope of the claims. I

Having thus fully described my invention what I claim as new and desire to secure by Letters- 'Patent is:

l. A jaw for a press, said jaw comprising two pairs'of oppositely disposed blocks positioned adjacent one another and joined by a toggle mechanism, said jaw being adapted to receive and clamp a metal strip between said pairs of blocks when said mechanism is tightened said blocks having plain smooth surfaces at positions where they grip the strip, the blocks of each pair having ey lindrical grooves, cylindrical members in, said grooves joined together by rods to form said toggle mechanism in order to permit one of the blocks of each pair to move in a parallel plane away from and toward the other block of the pair.

2. In combination, a jaw comprising inner rows of oppositely disposed blocks to form pairs positloned adjacent one another and adapted to reoeive a metal strip between the rows of blocks, outer rows or blocks disposed adjacent the opposite ends of each inner pair of blocks, and toggle mechanisms including cylindrical grooves in said blocks, cylindrical elements rotatably mounted in said grooves and joined together by rods for permitting the inner rows of blocks to move toward one another in parallel relation when tension is appl ed to the strip, whereby the blocks firmly grip the strip.

3. In combination. a jaw comprising inner rows of oppositely disposed blocks to form pairs positioned adjacent one another and adapted to receive, a metal strip between the rows of blocks, outer rows of blocks disposed adjacent the opposite ends of each inner pair of blocks, and pairs of toggles connecting adjacent inner and outer blocks for moving the inner rows of blocks in a direction parallel to the direction of the metal strip in order to cause the inner rows of blocks to move away from one another in a direction at right angles to the direction of the strip whereby the strip can be removed from the jaw, saidtoggles including a plurality of cylindrical elements joined together by rods and rotatably mounted in grooves formed in said blocks.

4. In combination, a jaw comprising a rail member having a groove along the length of the rail and containing an inner and an outer set of jaw blocks, each set comprising two rows of to receive a strip of metal, the outer set of blocks a being in contact at the side and bottom with said groove, yielding means for holding the inner row or blocks from the bottom of the groove, the inner and outer sets 01 blocks being secured together in pairs by toggle mechanisms arranged parallel with each other, said mechanisms including cylindrical grooves in the inner and outer blocks adapted to receive cylindrical elements joined together by rods, and common means engaging the inner blocks for causing the inner set a of blocks to be moved toward the bottom 01! the groove in order to separate the blocks of the inner set from one another and to permit the metal strip to be withdrawn from the j aw.

5. In combination, a jaw comprising a rail member having a groove along thelength of'the rail and'containing an inner and an outer set of Jaw blocks, each set comprising two rows of blocks, said inner rows or blocks being adapted to receive a strip of metal, the outer set of blocks beingin contact at the side and bottom with said groove, yielding means for holding the inner row of blocks from the bottom of the groove, the inner and outer sets of blocks being secured together by toggle mechanism, and means including bolts passing between the inner and outer sets of blocks and secured to a rigid bar for causing the inner set 01' blocks to be simultaneously moved toward the-bottom of the groove so as. to cause separation of the blocks of the inner set from one another and thus to open the law.

6. In combination, a law comprising a rail member having a, rectangular groove along the length of the rail and provided with spaced ledges,

said groove containing an inner and an outer set of jaw blocks, each set comprising two rows of rectangular blocks, the two inner rows of blocks being adapted to receive a metal strip between t the blocks, the outer set of blocks resting on said ledges, yielding means for holding the inner set of blocks away from the bottom oi the groove, the inner and outer sets of blocks being held together by toggle mechanism, and means including bolts for causing the inner set 0f.b10cks to be moved toward the bottom of the groove in order to separate the blocks of the inner set from one another and to permit the removal of the metal strip from the jaw, said bolts having heads which bear against only the inner set of blocks.

'7. A jaw for a press, said jaw comprising a plurality of pairs of oppositely disposed blocks comprising inner and outer blocks and positioned adjacent one another and adapted to receive a metal strip between each pair of blocks, and ad-' justable means engaging the inner block oieach pair for individually adjusting each pair of oppositely disposed blocks to vary the relative values of the forces exerted by the respective pairs of blocks.

8. In combination, a jaw comprising inner rows of oppositely disposed blocks to form pairs positioned adjacent one another and adapted to receive a metal strip between the rows of blocks,

outer rows of blocks disposed adjacent the opposite ends of each'inner pair of blocks, means connected between the outer row of blocks and the adjacent inner row of blocks for causing the inner rows of blocks to move toward one another when tension is applied to the strip, whereby the blocks-firmly grip the strip, and means for individually adjusting the position or the blocks'in the inner row of blocks in orderto control the relative clamping forces applied by the individual I 11 pairs or inner rows or blocks on the metal strip.

V 9. In combination, a jaw comprising inner rows of oppositely disposed blocks to form: pairs positioned adjacent one another and adapted to re- :ceivea metal strip between the rows of blocks, outer rows of blocks disposed adjacent the opposite ends of each inner pair of blocks, means in- 3 cluding toggle mechanism connected between the 1 outer'row 01 blocks and the adjacent inner row of blocks for causing .the inner rows of blocks to move toward one another when tension is applied 1 to the strip, whereby the blocks flrmly grip the b 3 strip,and means-tor individually adjusting the b position 01 the blocks in the inner'row of blocks 1 in order to control the relative clamping forces 1 applied by the inner rows Of blocks on-the metal I 1 strip, said last-mentioned means comprising bolts each passing through a respective block of the inner rows and adapted to be turned down to cause each block-of the inner row to rotate about the toggle mechanism and thus to vary the clamping 1 pressure exerted by consecutive pairs of the inner I rows of blocks.

10. In combination, a jaw comprising inner rows of oppositely disposed blocks to form pairs positioned adjacent one another and adapted to I receive a metal strip between the rows of blocks, outer rows of blocks disposed adjacent the opposite ends of each inner pair of blocks, means including toggle mechanism connected between the outer row of blocks and the adjacent inner row 1 of blocks for causing the inner rows of blocks to move toward one another when tension is ap- I plied to the strip, whereby the blocks firmly grip the strip, means for individually adjusting the innerqrows and adapted to *beturned down to member into clamping position-in said one direction, and releasing means operable to move at I least'one said member against the actionoi said position of the blocks in the inner row of blocks 1 in order to control the relative clamping forces applied by the inner rows of blocks on the metal j strip, said last-mentioned means comprising bolts 1 each passing through a respective block of the cause each block of the inner rowto rotate about 1 the toggle mechanism and thus to vary the clampf ing pressure exerted by consecutive pairs of the inner rows of blocks, and means for locking each adjusting bolt in its adjusted position of rotation.

, 11. A clamp comprising two pairs of oppositely disposed blocks positioned adjacent one another 1 and joined by a toggle mechanism, said jaw being .50 1 tween pairs of blocks when said mechanism is tightened, the blocks of each pair having cylindrical grooves, cylindrical; members in said grooves joined together by rods to form said togadapted to receive-and clamp a metal strip begle mechanism in order to permit one of the blocks. of each pair to move in a parallel plane I away from and toward the other block of the pair.

12. A clamp comprising a plurality of oppositely disposed pairs of blocks, all arranged endwise, the blocks of each pair being connected ,13.- In a clamp, a base, a pair of adjacent jaw members adapted to grip a work piece therebetween against movement in one direction, means pivotally connecting each said memberwith saidbase, including parallel links, each link extendin inwardly and away irom said one direction, means carried by said base urging each jaw rod slidably supported in. said base and engaging said one member to move the same against the" action of said urging means. r 14. In a clamp; a base, a pair of adjacent block members adapted to grip a part-therebetween when a force is applied to said part in a flrst. direction, a parallelogram linkage pivotally connecting each blockmember to said base, said linkage comprising links extending inwardly and away from sald'direction, and meansadapted to separate said members, said means comprising tension members extending through said base each tension member having a part engaging-a respective block member, and means connecting said tension members for simultaneous movement in a second direction opposite to said that direc-- tion. 7 15. In a clamp, a bas'e,a pair of adjacent jaw members adapted "to grip a work piece therebetween, against movement in one direction, means pivotally connecting each said member with said 7'.

base, said means including links extending inwardly and away from said one direction, yielding means carried by said base urgin each said yielding means, said releasing means comprising a bolt rotatably and slidably supported in said base and engaging said one member, and an actuating barwith which said bolt is threadedly engaged whereby said her is operable to move, said one member into work-releasing position. f 16. In a'clamp, a basehaving a substantially horizontal, upwardly opening channel therein, an

inner row of independent jaw members in said channel, an outer row of independent jaw. bersin said channel adjacent said inner row, the 7 corresponding member of each row forming a pair, said'pairs being adapted to grip a work piece therebetween, links pivotally connecting saidjaw members with said base, each link ex tending inwardly and'downwardly in said channel whereby an upward force on said work piece 1 causes said links to apply a reaction urgingsaid 1 jaw pairs together,'and means slidably carried by saidbase adapted to engage and simultane: ously move each jaw member downwardly in work releasing direction. I

v 17. In a'clamp, a base having a substantially horizontal, upwardly-opening channel therein,

said channel having undercut side walls, a first.

inner row of jaws in said channel, a second inner row of jaws in said channel adjacent said first inner row, corresponding jaws of each'jrow form}.

ing a pair, said pairs being adapted to grip a workpiece therebetween, a, first outer row of blocks engaging one undercut side wall of said channel, a second outer row of blocksengaging the other undercut side wall of said channel, links pivotally connecting corresponding jaws and blocks of said first rows, links pivotally connect v in'g. corresponding jaws and blocks of said secondrows, all said links extending inwardly and down-Q wardly, headed bolts slidably and .rotatably" mounted in said base, each bolt having its head all said bolts threadedly engaging said bar wheremove all said pairs of jaws into work releasing position.

18. In a clamp, a base having substantially horizontal, upwardly-opening channel therein, said channel having undercut side walls, a first inner row of blocks in said channel, a second inner row of blocks in said channel adjacent said first row, the corresponding opposed blocks of each row forming a pair, said pairs being adapted to grip a work piece therebetween, a first outer row of blocks engaging one undercut side wall of said channel, a second outer row of blocks engaging the other undercut side wall of said channel, links pivotally connecting corresponding blocks of said first row, links pivotally connecting corresponding blocks of said second row, all said links extending inwardly and'downwardly, headed bolts slidably and rotatably mounted in said base, each bolt having its head in engagement with a corresponding block of said first and second ro'ws only, a bar beneath said base, all said bolts threadedly engaging said bar whereby the relative clamping forces of said blocks in said first and second rows may be varied, means provided in the base operable to move said bar downwardly to move all said pairs of blocks into work releasing position, and means carried by said base for urging the blocks of said first and second rows upwardly into work clamping position.

19. In a clamp, a base channeled to have side and bottom walls, a pair of blocks adjacent the respective side walls of said channel and fixed against movement out of said channel, a pair of jaws in said channel between said blocks and adapted to be moved toward each other to grip a work piece therebetw'een, each jaw forming a pair with its respective block, there being cylindrical apertures in each pair opening into the adjacent sides of each pair ofblocks, each aperturev having its axis parallel to said channel, a rod section rotatably fitting each aperture, and links extending diametrically through and connecting corresponding sections of each pair, said links extending. downwardly and inwardly whereby tension applied to a work piece between said jaws causes a reaction on said links and a resulting clamping pressure on said jaws.

PAUL E. FLOWERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENT 

